Peroxycarboxylic acids are increasingly used as biocides in various fields owing to their broad biocidal efficacy and excellent environmental profiles. The most commonly used peroxycarboxylic acid is peracetic acid. Peracetic acid is a colorless, freely water soluble liquid which has great biocidal efficacy toward various microorganisms, such as bacteria, virus, yeast, fungi and spores. When decomposed, peracetic acid results in acetic acid (vinegar), water and oxygen. Pure peroxycarboxylic acids, such as peracetic acid, however, are unstable and explosive, and thus commercially available peroxycarboxylic acids are usually sold in an equilibrium solution. In addition to the peroxycarboxylic acid, an equilibrium solution also contains the corresponding carboxylic acid, hydrogen peroxide and water. Compared to the peroxycarboxylic acid, hydrogen peroxide only has negligible biocidal efficacy, but may pose environmental issues in some applications if it exceeds the specific release limitation. Furthermore, it has been disclosed that the presence of hydrogen peroxide has negative impacts on the efficacy of peroxycarboxylic acid toward some microorganisms.
In applications such as water treatment for use in fracturing drilling of oil and gas wells, the hydrogen peroxide that is in the peroxycarboxylic acid compositions may interact with other components used in the applications, such as gelling agents, friction reducers, corrosion inhibitors and scale inhibitors, etc. The presence of hydrogen peroxide in these solutions may cause the performance failure. Thus, there is a need to develop a peroxycarboxylic acid composition which has as high as possible peroxycarboxylic acid to hydrogen peroxide ratio for applications as a biocide in general, and in particular for water treatment in oil and gas drilling.
Commercially available peroxycarboxylic acid compositions generally have significantly less, or roughly equal, weight amounts of peroxycarboxylic acid than hydrogen peroxide. It is known that among other factors, the ratio of hydrogen peroxide to peroxycarboxylic acid plays a significant role in the stability of the peroxycarboxylic acid compositions. The higher the ratio of hydrogen peroxide to peroxycarboxylic acid, the more stable of the composition. Some commonly available peroxycarboxylic acid compositions have a ratio of about 1.5 to 1 hydrogen peroxide to peroxycarboxylic acid. While compositions with higher ratio of peroxycarboxylic acid to hydrogen peroxide are commercially available, these compositions are in small packaging sizes limited by self accelerating decomposition temperature (SADT) transportation limitations and require controlled temperature storage due to the limited stability of the compositions.
Various stabilizers are used in peroxycarboxylic acid compositions to stabilize the compositions. For example, pyridine carboxylic acid based stabilizers, such as picolinic acid and salts, pyridine-2,6-dicarboxylic acid and salts, and phosphonate based stabilizers, such as phosphoric acid and salts, pyrophosphoric acid and salts and most commonly 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and salts, are used. When used individually at the right level, these stabilizers can significantly improve the stability of the peroxycarboxylic acid compositions, and for the conventional peroxycarboxylic acid compositions, the stability profile achieved with these stabilizers allows for the commercial use of these compositions. For peroxycarboxylic acid compositions with high ratios of peroxycarboxylic acid to hydrogen peroxide, the extra stability challenge cannot be met by these stabilizers used in the traditional matter.